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Glossary of water terms

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Adsorption
A physical process of a gas, liquid or dissolved substance being taken up by (or glued to) the surface of a solid.

Acre-foot
A term used to describe volumes of drinking or recycled water. One acre-foot equals 325,851 gallons of water, which is enough to serve the needs of two households of five, for one year. An acre-foot of water would cover an acre one foot deep.

Agriculture
The science, art and business of cultivating the soil, producing crops and raising livestock (farming).

Alluvial deposits
Rock, gravel, sand, silt and clay that have been carried and deposited by running water.

Artesian well
A well that produces a flow of water due to the pressure of underground water storage.

Appropriative rights
The right to take and beneficially use a specific quantity of water as granted by the state in accordance with California waterlaws.

Aquifer
An underground basin where water is stored after percolating down through many layers of rock and gravel. These basins are dark, and bacteria cannot live in them. The water in aquifers is clean and safe for drinking without adding any chemicals. Some of our drinking water is pumped out of aquifers. If aquifers were allowed to dry out, the ground would collapse just as if a chair were pulled out from under a student. (An aquifer is a body of rock that is sufficiently permeable to conduct groundwater and to yield economically significant quantities of water to wells and springs.)

In Santa Clara Valley, there are three aquifers: the Santa Clara basin and the Llagas and Coyote sub-basins.

Aquitard
A geological formation that will not transmit water quickly enough to fill a well,practically, but may store some quantities of water.

Basic user charge
A charge levied on every acre-foot of water pumped from the groundwater basin or delivered by the SCVWD to recover costs incurred for the benefit of current users.

Bay
A body of water partially enclosed by land, but with a large outlet to the sea or ocean.

Beltpress
A device for reducing the liquid content of treatment plant sludge.

Concrete-lined channel
A flood control or water conveyance channel with the sides and bottom made of concrete.

Confined aquifer
An aquifer overlain by material sufficiently impervious to retain groundwater in the aquifer under pressure.

Conjunctive use
The planned use and storage of surface and ground water supplies to improve water supply reliability.

Connate water
Water that was trapped in a geologic formation at the time the formation was deposited. If the formation was deposited in the ocean or a saline lake, the connate water is also saline.

Conservation
The act of protecting from loss or depletion.

Contamination
An impairment of the quality of water by microorganisms, chemicals, sewage or industrial waste which renders water unfit for its intended use. In California, this means the water poses an actual hazard to public health.

Cubic feet per second
A unit of measurement for flowing water; the number of cubic feet of water that passes by a given point in a second.

Dam
A structure built to hold back water. Specific kinds of dams include:

Sack dam:
Sack dams were used in early experiments. The sack dams were merely burlap sacks filled with whatever earth material was available, laid snugly side by side, layer on layer, at irregular intervals over the gravel streambeds. These dams served their purpose in their first year of use, but deteriorated over time. The high cost of replacing them led to their discontinuation in the late 1920s.

Sausage dams:
Sausage dams were constructed of rock and strips of heavy gauge "box type" construction wire. Strips of wire matter were laid across the stream, then rock was placed on and between the layers of the wirematting. This method of construction provided a stable dam and served the purpose of spreading water over larger areas for percolation. However, it was expensive and was eventually discontinued.

Rock dams:
Experiments with rock dams proved successful and less expensive than sausage and sack dams. A mound of rocks spread across the stream about one or two feet high is sufficient to slow the flow of water and allow spreading and percolation of water.

Check dams:
Check dams were small structures of loose rock, logs, brush and occasionally concrete built in a series of mountain canyons to regulate and prolong the flow of rainwater descending through the watershed. Dams also can be built out of concrete. When builders constructed the huge dam at Shasta Lake, they poured concrete for 24 hours straight, seven days a week, for 51/2 years!

Developed water
Water that is controlled and managed (dammed, pumped, diverted, stored, etc.) for a variety of uses.

Disinfection
A cleansing of harmful chemicals.

Dissolved oxygen (D.O.)
The oxygen dissolved in water. It is necessary for aquatic life.

Drought
A long period with little or no rain.

Dry farming
Farming without irrigation, using only the water which falls naturally in the form of rain to water crops.

Earth channel
A flood control or water conveyance channel with sides and bottom composed of earth.

Effluent
Treated wastewater. If effluent has been treated to a high enough standard, it may be considered "reclaimed" or recycled.

Electrical conductivity
A measure of the ability of the water to conduct electrical current. It is used as a measure of the dissolved solids in the water.

Endangered species
A species which is threatened with extinction.

Environment
One's surroundings.

Environmental impact report (EIR)
A report required by the California Environmental Quality Act to describe the environmental impact of a proposed project.

Environmental impact statement (EIS)
A report required by the federal Environmental Protection Act to describe the environmental impact of a proposed federal project.

Estuary
The shallow water areas of bays or the mouths of rivers and creeks. This is the place where ocean tides meet and mix with fresh water.

Evaporation
The process by which surface or subsurface water is converted to atmospheric vapor.

Fault
A break in the continuity of rock formation caused by shifting in the earth's crust.

Filtration
The process of filtering, or removing constituents from a substance.

Floodplain
The relatively flat area adjoining a river or lake that may be covered with water during a flood.

Geology
Scientific study of the origin, history and structure of the earth.

Groundwater
Water that has seeped beneath the earth's surface down through soil materials to become groundwater. This is accomplished naturally by rainfall and also artificially by humans. See percolation ponds.

Grubbing
Derived from the word "grub," which means to root out or uproot; trees are cut and removed, then stumps and roots are grubbed out. Grubbing includes removing large, long-rooted vines, which also must be uprooted and cleared away. Trees are moved to safe areas and firewood is made available free to the public or burned.

Headwater
The source or sources and upper part of a stream, especially of a large stream or river.

Hydrologic cycle (also called the water cycle)
The movement of water as it evaporates from rivers, lakes or oceans, returns to the earth as precipitation, flows into rivers and evaporates again.

Imported water
Water that is moved from one drainage basin to another. For example, water moved from the Sacramento Valley to the San Joaquin Valley through canals and pipelines into the Santa Clara Valley. This area uses more water than it naturally has, so water must be imported to fulfill the needs of the large population.

Irrigation
Diverting or moving water from its natural course in order to use it.

MGD
Abbreviation for million gallons per day. This term is used to describe the volumes of wastewater treated and discharged from a treatment plant.

Marsh
An area of low-lying wetland.

Nitrification
To treat or combine with nitrogen.

Nonpoint pollution
A source of pollution that is general, not localized. An industrial plant might emit localized pollution, but the various types of trash which flow down storm drains from the streets of the Santa Clara Valley to San Francisco Bay cannot be tracked. This is nonpoint pollution.

Percolation pond
A pond that allows water to percolate (or seep) through layers of rock and gravel. The water is cleaned as it slowly travels downward and eventually reaches an underground aquifer. The purpose of man-made percolation ponds is both to clean the water and to keep the ground from sinking.

Potable water
Water that meets drinking water standards.

Pond
A still body of water smaller than a lake.

Recycled water
Water that has gone through a sewage treatment plant and is then re-used for irrigation or other purposes.

Reservoir
A large storage area for water.

Retrofit
The process for constructing and separating new potable and recycled pipelines that allow recycled water to be used for non-drinking purposes. A retrofit system separates recycled water from drinking water pipelines.

Riparian habitat
The vegetation and wildlife found along the shores of streams, rivers and lakes.

Riparian rights
The legal right which assures an owner of land adjacent to a creek or natural body of water the reasonable use of that water.

River
A large, natural stream of water that empties into a large body of water such as a lake or the ocean.

Runoff
During back-to-back rains, some water is not immediately soaked up by the ground. This water is called runoff.

Salinity
The concentration of salt dissolved in water.

Saltwater seepage
When saltwater makes its way into an aquifer, contaminating the freshwater with salt.

Sludge
The settled solids containing enough water to form a semi-liquid mass that comes from treatment processes in sewage, reclamation and freshwater plants.

Spring
A place where groundwater flows naturally from a rock or soil onto the land surface or into a body of surface water.

Stream
A body of running water.

Surface water
The water that rests on top of the earth in streams, lakes, rivers, oceans and reservoirs.

Tertiary
A high level of wastewater treatment that repurifies the water to meet state health requirements.

Valley
An area of low land surrounded by hills or mountains.

Water reclamation
The treatment and management of wastewater to produce water of suitable quality for additional use.

Water supply
The water available for an area or community.

Water quality
The chemical, physical and biological properties of water that affect its suitability for use.

Wastewater
Used water that comes from homes and businesses.

Watershed
The area of land over which rain falls and then drains off on its journey to the ocean, or into reservoirs for storage.

Watershed management
A widely used phrase associated with studies, programs and policies, under-taken to protect and/or define the acceptable uses of drainage basins and their receiving waters.

Water supply
The water available for an area or community.

Water table
The top of the water within an unconfined aquifer.

Weir
A dam made of wood, concrete, rocks, steel or similar material places on the bottom of a stream channel in a watercourse to control the flow of water; a dam in a waterway or conduit used to control the water level or the flow; a structure over which liquids flow and which is used to measure the rate of flow.